How to get all the methods of an object using JavaScript ?

An HTML document contains some methods and the task is to get all methods of the object. There are two methods to solve this problem which are discussed below:

Approach 1:

• Create a function that takes an object as input.
• Use typeof operator, which checks if the type of object is a function or not.
• If the type of object is a function then it returns the object.

Example: This example implements the above approach. 

html

<script src=
"https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js">
</script>
<h1 style="color: green">
    GeeksforGeeks
</h1>

<p id="GFG_UP">
</p>

<button onclick="gfg_Run()">
    Click Here
</button>

<p id="GFG_DOWN">
</p>

<script>
    var el_up = document.getElementById("GFG_UP");

    var el_down = document.getElementById("GFG_DOWN");

    el_up.innerHTML = "Click on the button to get "
                + "the all methods of any Object.";

    function Obj() {
        this.m1 = function M1() {
            return "From M1";
        }
        this.m2 = function M2() {
            return "From M2";
        }
    }

    function getAllMethods(obj = this) {
        return Object.keys(obj)
            .filter((key) => typeof obj[key] === 'function')
            .map((key) => obj[key]);
    }

    function gfg_Run() {
        el_down.innerHTML = getAllMethods(new Obj());
    }
</script>

Output:

 Get all the methods of an object

Approach 2:

• Create a function that takes an object as input.
• Use typeof operator, which checks if the type of object is a function or not. This example also checks if any error occurred or not and if occurred then handle it properly.
• If the type of Object is a function then return it.

Example 2: This example implements the above approach. 

html

<script src=
"https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js">
</script>
<h1 id="h1" style="color: green">
    GeeksforGeeks
</h1>
<p id="GFG_UP">
</p>
<button onclick="gfg_Run()">
    Click Here
</button>
<p id="GFG_DOWN">
</p>
<script>
    var el_up =
        document.getElementById("GFG_UP");
    var el_down =
        document.getElementById("GFG_DOWN");
    el_up.innerHTML =
    "Click on the button to get the all methods of any Object.";

    function Obj() {
        this.m1 = function M1() {
            return "From M1";
        }
        this.m2 = function M2() {
            return "From M2";
        }
    }

    function getAllMethods(obj) {
        var result = [];
        for (var id in obj) {
            try {
                if (typeof(obj[id]) == "function") {
                    result.push(id + ": " + obj[id].toString());
                }
            } catch (err) {
                result.push(id + ": Not accessible");
            }
        }
        return result;
    }

    function gfg_Run() {
        el_down.innerHTML = getAllMethods(new Obj()).join("\n");
    }
</script>

Output:

 Get all the methods of an object